Mr Boyd Barrett made his comments during a heated four hour DÃ¡il debate on the plan to join the Pesco. The Opposition said there was no rush and there should be a full debate with Army and other experts being called in to give a detailed analysis.

Opposition TDs called on the Independent Alliance to make their positions clear before the Government voted on the move. Independents4Change TD Clare Daly said Ministers of State Finian McGrath and John Halligan in particular, should do so when they had in opposition been vehemently opposed to the militarisation of Europe and an EU army.

But TÃ¡naiste Simon Coveney who opened the debate rejected the claims that Ireland would be joining an EU army by supporting a new European military structure or that the proposal will breach Irelandâs neutrality.

Mr Coveney insisted that the Stateâs âtraditional policy of military neutrality is not going to changeâ.

The TÃ¡naiste claimed some TDs were trying to turn Pesco into something more than it was. Ireland would opt in or opt out on a voluntary basis to missions, he said.

These would be in the areas peacekeeping, counter-terrorism, training and marine surveillance.

But Mr Boyd Barrett described this as âcynical rubbishâ and said the move is an âabandonment of our neutrali ty and is unconstitutional and should be challengedâ.

He said âwe will have to seriously consider a constitutional challengeâ.

He said the process was very cynical he said the Government knew and had decided on Pesco but did not tell the business committee, a majority of which opposed the issue being voted on on Thursday.

EU values

Fianna FÃ¡il defence spokeswoman Lisa Chambers sai d that in a post-Brexit scenario âit is extremely important that we as a member state show our support for the EU and its valuesâ.

She could not understand âhow anybody could suggest that this is somehow joining a European armyâ. But she said there should be ongoing debate on the role of the Defence Forces and the Department of Defence should update the Oireachtas on a quarterly basis about the engagements the State was involved in and the costs.

The Mayo TD believed increased spending on defence would force the department to fund and resource the Defence Forces and that the spending was on research for areas such as surveillance and not about making weapons.

The TÃ¡naiste had earlier said there was âsome misunderstandingâ over funding. âThere is absolutely no commitment to increase defence spending to 2 per cent of GDP.â

He said the 2 per cent solely reflected a collective commitment of 2 per cent of defence spending to be used for research.

But Ms Daly said estimates suggested the Government would be paying â¬1.3 billion by 2021 and that was âgallingâ at a time when Defence Force personnel were dependant on social welfare to make ends meet.

He said the proposal was in âdirect violation of Article 29.4.9 of the Constitution. The provision holds that a Government cannot adopt any EU decision that would create a European common defence.â

âEuropean armyâ

Labour TD Brendan Ryan said his party leader Brendan Howlin had asked for a debate on the issue in June. He said the EU video on Pesco was like a movie trailer âglorifying military expenditure on weaponsâ.

Mr Ryan said âwe donât want Ireland clipped onto the tail of this wagonâ and dragged irreversibly into a modernised European army.

Green party leader Eamon Ryan said the proposal went far beyond increasing cooperation. âThis is about building a military and industrial armaments capability that will not provide security in the long run.â